refund

If the exception is related to a Refund, this will return one of two things:

1. The updated Refund with a Refund.status of failed. This signifies that there was a failure to process this refund, and Terminal.processRefund should be retried to try refunding to another payment method.

2. Null. This signifies that the request to Stripe's servers timed out and Refund.status is unknown. In this situation, the call to Terminal.processRefund should be retried with the original RefundParameters.

For exceptions unrelated to a Refund, this will return null.